1. Field of the Invention
The present invention relates to a cleaning apparatus that is used in an image forming apparatus such as a copy machine or printer, and also relates to an image forming apparatus that is provided with this cleaning apparatus.
Priority is claimed on Japanese Patent Application No. 2009-295799, filed Dec. 25, 2009 and Japanese Patent Application No. 2009-295800, filed Dec. 25, 2009, the contents of which are incorporated herein by reference.
2. Description of Related Art
In an image forming apparatus such as a copy machine or printer, a photosensitive drum is provided in an image forming section. An electrostatic latent image is formed on the surface of this photosensitive drum, and toner is then adhered thereto resulting in a toner image being formed.
The toner image is then transferred onto a transfer body such as copy paper, however, the toner does not get completely transferred and a portion thereof may remain on the surface of the photosensitive drum. Alternatively, electrical discharge product that is produced during the forming of the electrostatic latent image may remain adhered to the surface of the photosensitive drum. This residual toner or electrical discharge product prevents (impedes) the forming of new images, and is a main cause for superior transfer images not being obtained. Because of this, a cleaning apparatus that is used to remove adhesion material (i.e., toner, electrical discharge product, and the like) from the surface of the photosensitive drum is provided in the image forming apparatus.
FIG. 5 is a schematic cross-sectional view of a conventional cleaning apparatus.
In a cleaning apparatus (a) there are provided a cleaning blade (c) that scrapes adhesion material from the surface of the photosensitive drum (b), a cleaning roller (d) that rotates while in contact with the photosensitive drum (b), and a collect screw (e) that collects (recovers) the removed adhesion material.
The cleaning roller (d) that is in contact with the photosensitive drum (b) not only has a function of removing toner, but also has functions of holding toner so as to form a toner layer on the surface of the cleaning roller (d), and polishing the surface of the photosensitive drum (b).
However, in the conventional cleaning apparatus (a), because the amount of toner held on the cleaning roller (d) is not constant, keeping the thickness of the toner layer formed on the surface of the cleaning roller (d) uniform has proved problematic. Accordingly, in the cleaning apparatus (a) having the above described structure, it has not been possible to consistently polish a photosensitive drum.
In order to solve the above described problem, a cleaning apparatus has been developed in which toner that has been removed from the photosensitive drum by a cleaning blade is accumulated (collected) in a toner receive (receive member, receptacle) that is provided underneath the cleaning roller.
In this apparatus, toner remaining on the surface of the photosensitive drum is scraped off using a cleaning blade, and the scraped off toner is accumulated in a toner receive that is provided underneath the cleaning roller, and the collected toner is then held on the cleaning roller so that the surface of the photosensitive drum can be polished.
By providing the toner receive underneath the cleaning roller, a sufficient quantity of toner can be supplied to the cleaning roller to be held thereon, so that the polishing effect can be improved as a result.
However, if an excessive quantity of toner is adhering to the surface of the photosensitive drum, the quantity of toner that is accumulated in the toner receive also becomes excessive, and there is a possibility that the quantity of toner held on the cleaning roller will become too great and will re-adhere to the photosensitive drum. Moreover, if the toner quantity adhered on the surface of the photosensitive drum is too small, then sufficient polishing cannot be achieved and it becomes necessary to supply toner.
Accordingly, because the polishing effect varies as the toner quantity increases and decreases, it is difficult to achieve consistent polishing.
In contrast, a cleaning apparatus has been developed that is provided with a toner receive that is provided underneath the cleaning roller, and with a scraper that is used to scrape off toner held on the cleaning roller.
In this apparatus, toner accumulated in the toner receive is held on the cleaning roller, and the toner is scraped off using a scraper so that the toner quantity can be adjusted.
Because it is thus possible to supply a sufficient quantity of toner to the cleaning roller, and because the toner quantity can be adjusted by being scraped off, the quantity of toner held on the cleaning roller has no effect on the print coverage and the polishing effect is generally consistent (substantially unchanging).
However, there is a possibility that the above described scraper will remove too much of the toner held on the cleaning roller, and in this case the problem arises that friction between the cleaning roller and the scraper causes the toner to become fused to the respective members.
Furthermore, if this apparatus is used for a lengthy period of time, the problems arises that portions of the scraper become worn away and uniform polishing is no longer possible. Namely, as a result of portions of the scraper being worn away, it is no longer possible to adjust the quantity of toner on the cleaning roller and the thickness of the toner layer on the cleaning roller increases. Because of this, the polishing of the surface of the photosensitive drum becomes excessive.
Moreover, because the toner layer is thinner in those areas which are scraped by the non-worn portions of the scraper than those in areas which are scraped by the worn portions of the scraper, the pressing force with which the cleaning roller presses against the photosensitive drum is reduced and sufficient polishing is not possible. Accordingly, it is difficult to consistently polish a photosensitive drum over an extended period of time.